The behaviour of the D-region at mid-latitudes during a sudden ionospheric disturbance

Abstract

The ‘full-wave’ integration technique is used to deduce, from observations of the propagation of l.f. and v.l.f. radio waves, the changes which take place in the height distribution of electron density during a ‘sudden ionospheric disturbance’ Two S.I.D.s have been studied, the first is an ‘average’ S.I.D. which gives rise to most of the observed characteristics of the propagation of the radio waves and the second is an S.I.D. which occurred on 7 October 1948, during which continuous measurements were made at Cambridge of the strength and phase of downeoming waves at 16 and 70 kc/s at steep incidence. During the latter S.I.D. the electron density increased at all heights from 65 to 80 km by factors of 1·2, 2·4, 5·8 and 4·0 at heights of 65, 70, 75 and 80 km respectively.